Blast resistant structural building element

ABSTRACT

One embodiment is directed to a blast resistant building element having a compressed polymeric foamed core, the element including an internal track having an internal track web integrally connected to a pair of spaced apart and outwardly extending internal track sidewalls so as to define a first generally U-shaped profile, a surrounding track having a surrounding track web integrally connected to a pair of spaced apart and outwardly extending surrounding track sidewalls so as to define a second generally U-shaped profile and a compressed polymeric foamed core disposed within the internal track, wherein the compressed polymeric foamed core exerts a force against a portion of internal surfaces of the internal track and surrounding track.

CROSS-REFERENCE To RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/501,070 filed on Jun. 24, 2011, which application is incorporated herein by reference in its entirety for all purposes.

TECHNICAL FIELD

The present invention relates generally structural building elements used in the construction of buildings and more specifically to blast resistant structural building elements used in the construction of buildings.

BACKGROUND OF THE INVENTION

Structural building elements provide support, for example, in the framing of a building. Such building elements alone and in combination in a building are increasingly subject to strict codes that require them to be environmentally friendly while also providing substantial resistance to ballistic and explosive threats related to terrorist activities. Leadership in Energy and Environmental Design Green Building Rating System (LEED) building standards provide one example of codes related to environmentally friendly building materials and buildings. Additionally, UFC 4-010-01 DoD Minimum Antiterrorism Standards for Buildings provides one example of a code related to ballistic and explosive resistant building materials and buildings.

Metal framing assemblies used to construct commercial and residential buildings are common in the building construction arts. These metal framing assemblies are generally constructed from a plurality of metal framing members including studs, joists, trusses, and other metal posts and beams formed from sheet metal and frequently fabricated to have the same general cross-sectional dimensions as standard wood members used for similar purposes. Metal framing members are typically constructed by roll-forming 12 to 24 gauge galvanized sheet steel. Although many cross-sectional shapes are available, the primary shapes used in building construction are C-shaped studs and U-shaped tracks.

Some building elements comprise pairs of tracks that are mated (see, e.g., U.S. Pat. No. 3,420,032 to A. E. Felt; www.scafco.com; www.proxheader.com; and www.clarkdietrich.com). Such assemblies may include an internal portion that may remain empty or be filled. For example, hollow sheet metal building assemblies may be constructed and filler may be injected into the hollow portion before or after the assembly is incorporated into a building. Such a method of producing a sheet-metal building assembly is deficient because the filler is typically unevenly distributed, leaving gaps between the filler and sheet-metal assembly. This creates a building material that has poor and uneven thermal transfer profiles and which has reduced and uneven strength. Hollow products fail to provide insulation and increased strength created by an insulation bonding process. Additionally, in the abovementioned products, none have manufactured insulation included in their design and all require end user insulation installation.

Further sheet-metal building elements comprise a pair of tracks with a core that is not injected (see, e.g., U.S. Pat. No. 5,678,381 to DenAdel and U.S. Pat. Pub. 2007/0113506 to Denadel). For example, an insulative member fills the space between two elongated U-shaped tracks, with a space between the tracks that exposes a portion of the insulative material. Such products that do not fully surround the core fail to provide adequate strength as a building product and expose the core to potential damage.

While numerous metal framing assemblies exist in the art, few if any address the need for building materials that meet and exceed both environmental and anti-terrorism building standards. Thus, there is still a need in the art for new and improved metal framing assemblies and associated methods of making such assemblies. The present invention fulfills these needs and provides for further related advantages such as meeting current energy codes.

SUMMARY OF THE INVENTION

In brief, the present invention in one embodiment is directed to a blast resistant building element having a compressed polymeric foamed core, the element including an internal track having an internal track web integrally connected to a pair of spaced apart and outwardly extending internal track sidewalls so as to define a first generally U-shaped profile, a surrounding track having a surrounding track web integrally connected to a pair of spaced apart and outwardly extending surrounding track sidewalls so as to define a second generally U-shaped profile and a compressed polymeric foamed core disposed within the internal track, wherein the compressed polymeric foamed core exerts a force against a portion of internal surfaces of the internal track and surrounding track.

Another embodiment is directed to a method of constructing a blast resistant building element having a compressed polymer foamed core, the method including bending a first elongated sheet-metal piece to form a surrounding track, having a surrounding track web integrally connected to a pair of spaced apart and outwardly extending surrounding track sidewalls to thereby define a first generally U-shaped profile, bending a second elongated sheet-metal piece to form an internal track having an internal track web integrally connected to a pair of spaced apart and outwardly extending internal track sidewalls to thereby define a second generally U-shaped profile, applying an adhesive to at least one of the surfaces within the generally U-shaped internal track, positioning a block of foamed polymer within the first generally U-shaped internal track, the block of foamed polymer being slightly larger than the space defined by the internal track web and its pair of spaced apart and outwardly extending internal track sidewalls, positioning the surrounding track about the internal track, and compressing the tracks together to yield the blast resistant building element having the compressed polymer core.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a illustrates an exploded side perspective view of blast resistant structural building element assembly in accordance with one embodiment of the present invention.

FIG. 1 b illustrates a side perspective view of blast resistant structural building element assembly in accordance with the embodiment depicted in FIG. 1 a.

FIG. 2 a illustrates a side view of a blast resistant structural building element assembly in accordance with the embodiment depicted in FIGS. 1 a and 1 b.

FIG. 2 b illustrates a close-up side view of a portion of FIG. 2 a

FIG. 3 a illustrates an exploded side perspective view of blast resistant structural building element assembly in accordance with another embodiment of the present invention.

FIG. 3 b illustrates a side perspective view of blast resistant structural building element assembly in accordance with the embodiment depicted in FIG. 3 a.

FIG. 4 a illustrates a side view of a blast resistant structural building element assembly in accordance with the embodiment depicted in FIGS. 3 a and 3 b.

FIG. 4 b illustrates another side view of a blast resistant structural building element assembly in accordance with the embodiment depicted in FIGS. 3 a and 3 b.

FIG. 5 a illustrates a side view of an example of a blast resistant structural wall assembly comprising a pair of blast resistant structural building element assemblies in accordance with two embodiments.

FIG. 5 b illustrates a side view of another example of blast resistant structural wall assembly comprising a pair of blast resistant structural building element assemblies in accordance with two embodiments.

FIG. 6 illustrates a method of making a blast resistant structural wall assembly in accordance with an embodiment of the invention.

FIG. 7 a and FIG. 7 b illustrates two embodiments of a blast resistant structural wall assembly that were subject to strength tests.

FIG. 8 illustrates a table of results from strength tests of the assemblies of FIG. 7 a and FIG. 7 b having a summary of the gross and effective section properties including Allowable Moment (Ma) and Allowable Shear (Va) capacities of an entire family of assembly sections in 4-inch, 6-inch, and 8-inch depths.

DETAILED DESCRIPTION

Referring now to the drawings wherein like reference numerals designate identical or corresponding elements, the present invention in one embodiment is directed to a blast resistant structural building element assembly 100 that may be used for various construction purposes including framing of a building. The invention is further related to and a method of making a blast resistant structural building element assembly 100. FIGS. 1 a, 1 b, 2 a and 2 b depict a blast resistant structural building element assembly 100 in accordance with one embodiment and FIGS. 3 a, 3 b, 4 a and 4 b depict a blast resistant structural building element assembly 100 in accordance with another embodiment.

As depicted in FIGS. 1 a-4 b, an embodiment of the inventive blast resistant structural building element assembly 100 comprises an elongated sheet-metal surrounding track 105 that comprises a surrounding track web 110 integrally connected to (and flanked by) a pair of spaced apart and downwardly extending surrounding track sidewalls 115 (sometimes referred to as flanges or legs), which define a U-shaped surrounding track slot 155 having a surrounding track internal surface 145. The assembly 100 further comprises an elongated sheet-metal internal track 120 that comprises an internal track web 125 integrally connected to (and flanked by) a pair of spaced apart and downwardly extending internal track sidewalls 130 (sometimes referred to as flanges or legs), which define a U-shaped internal track slot 160 having an internal track internal surface 150. The assembly 100 further comprises a compressible core 135, which may comprise an elastic material such as polystyrene.

As best shown in FIGS. 1 b, 2 a, 2 b, 3 b, 4 a, and 4 b an assembled structural building element assembly 100 has the internal track 120 disposed within the surrounding track slot 155, with respective pairs of surrounding and internal track sidewalls 115, 130 positioned adjacent to each other and defining a first and second opposing sidewall face 165, 170 of the assembly 100. The internal track sidewalls 130 extend into the surrounding track slot 155 toward the surrounding track web 110, and the surrounding track sidewalls 115 surround the internal track sidewalls 130. The surrounding and internal track webs 110, 125 further define a first and second opposing web face 175, 180 of the assembly 100. The opposing sidewall faces 165, 170 are substantially parallel with respect to each other and the opposing web faces 175, 180 are substantially parallel to each other and define a substantially rectangular profile of the assembly 100.

The assembly 100 further comprises a plurality of pins 140 positioned on the sidewall faces 165, 170, which extend though one surrounding and internal sidewall 115, 130 and into the core 135. The pins 140 couple the surrounding and internal tracks 105, 120 along with the core 135, and are positioned along the length of the opposing sidewall faces 165, 170. The pins 140 are preferably nails, but may also be screws or another suitable coupling element.

The core 135 substantially fills the space within the surrounding and internal slots 155, 160. For example, the core 135 extends distance D1 between respective surrounding and internal track sidewalls 115, 130, and the core 135 extends distance D2 between the surrounding and internal web 110, 125. As best shown in FIG. 2 b, there may be an adhesive layer 210 between the core and the surrounding and internal tracks 105, 120. The adhesive layer may couple the core 135 within the surrounding and internal slots 155, 160.

In accordance with various embodiments, the assembly 100 may have different configurations. For example in the embodiment depicted in FIGS. 1 a, 1 b, 2 a and 2 b, the internal track 120 is positioned within the surrounding track slot 155 such that the surrounding track sidewalls 115 do not extend past the face 180 of the internal track web 125. In contrast, in the embodiment depicted in FIGS. 3 a, 3 b, 4 a and 4 b, the internal track 120 is positioned within the surrounding track slot 155 such that the surrounding track sidewalls do extend past the face of the internal track web 125.

In some embodiments, the core 135 may be different dimensions to provide for different configurations such as in the embodiments discussed above, where the size of the surrounding and internal tracks 105, 120 are substantially the same, but the core 135 is of a size which allows the core 135 to substantially fill the space within the surrounding and internal slots 155, 160, and allow the surrounding track sidewalls 115 to extend past the internal track web face 180 or not extend past the internal track web face 180.

In further embodiments, the length of the surrounding and internal track sidewalls 115, 130 may be any suitable length and the dimensions of the core 135 may also be any suitable length. For example, in one embodiment, an assembly 100 may have the internal track sidewalls 130 that extend toward and contact or nearly contact surrounding track web 110, and the core 135 may substantially fill the space within the surrounding and internal slots 155, 160, and the surrounding track sidewalls 115 may not extend past the internal track web face 180.

Referring now to FIGS. 4 a, 4 b, 5 a and 5 b, various embodiments of a structural building element assembly 100 may be used in a building wall assembly 500. FIGS. 5 a and 5 b depict an assembly 100 in accordance with the embodiment depicted in FIGS. 4 a and 4 b being used as a beam in and a further embodiment of a building element assembly 100 being used as a wall stud. For example, an infill stud 510 may couple with an assembly via pins 140 extending through respective surrounding track sidewalls 115 and into the infill stud 510. In one embodiment, as depicted in FIG. 5 b, the infill stud 510 may extend to and couple with a base track 530, which comprises anchorage points 540. The assemblies 100 may abut each other and be supported by a cripple study 520 and/or an angle connector 560.

The uses of a building element assembly 100 depicted in FIGS. 5 a and 5 b are simply examples, and various embodiments may be used and configured for any suitable portion of a building wall. Additionally, various embodiments of a building element assembly 100 may be sized to be analogous to standard dimensional lumber sizes or standard sheet-metal building material sizes and may be used like dimensional lumber or sheet-metal building materials.

Referring now to FIG. 6 an inventive blast resistant structural building element assembly 100 may be constructed by the method 600, which begins at step 610, where a first elongated sheet-metal piece is bent to form a surrounding track 105 having a web 110 and a pair of downwardly extending sidewalls 115 that define a slot 155. In step 620, a second elongated sheet-metal piece is bent to form an internal track 120 having a web 125 and a pair of downwardly extending sidewalls 130 that define a slot 160. For example, a sheet-metal bending brake may be used to form the internal and surrounding tracks 105, 120.

The method 600 continues at step 630, where adhesive is applied to at least one of the surrounding and internal track slots 155, 160. Various suitable adhesives may be used; however, a preferred adhesive is a moisture-activated urethane adhesive. The adhesive may be applied via a wand, brush, curtain, or other suitable method.

In step 640 an elongated assembly 100 is formed with the internal track 105 residing within the surrounding track slot 155 with a compressible core 135 residing within the slots 155, 160 so as to form a composite. In step 650, the assembly 100 and core 135 are compressed by applying force to opposing faces of the assembly 100. In step 660 the tracks 105, 120 are fixed by applying a plurality of pins 140 to the assembly 100 that extend through adjacent sidewalls, 115, 130 and into the core 135. For example, a press may be used to compress the assembly 100 via opposing web faces 175, 180, which may in turn compress the core 135. The surrounding and internal tracks 105, 120 may be fixed in position such that the core 135 remains at least partially compressed. The compressed core 135 may exert pressure on a portion of the internal track and surrounding track internal surfaces 145, 150, which may include the webs 110, 125 and/or the sidewalls 115, 130.

Compressing the core 135 and fixing the tracks so that core 135 remains compressed or such that the core 135 exerts pressure on the internal track and surrounding track internal surfaces 145, 150 may be desirable for various reasons. For example, the core 135 may thereby evenly spread the adhesive between the tracks 105, 120 and generate a more uniform adhesive layer 210. A compressed core 135 may further provide more uniform contact between the core 135 and tracks 105, 120, which can generate increases structural integrity and enhanced thermal transfer between the tracks 105, 120, adhesive layer 210 and core 135. Improved structural integrity and thermal transfer of the assembly 100 may provide for blast resistant properties as described in the Example section below. In an embodiment, the core 135 may be oversized by about approximately 0.5%, 1%, 3%, 5%, 9% or the like, in one or more dimensions.

The pins 140 may be inserted at a suitable interval along the sidewall faces 165, 170. The pins 140 are preferably nails, but the pins 140 may be screws or other suitable coupling element. In some embodiments, pins 140 need not be present, and the surrounding and internal tracks 105, 120 may be fixed or coupled via an adhesive, welding or other suitable means.

For purposes of illustration and not restriction, the following Example demonstrates various aspects and utility of the present invention.

EXAMPLE 1

Several mockups of a blast resistant structural building element assembly in accordance with several embodiments of the present invention were constructed and tested to evaluate the assembly's strength, durability and failure characteristics.

The tests were configured in accordance with the American Iron and Steel Institute Testing Standard AISI 911-08. The test specimens consisted of 10-foot, 6-inch long assembly sections of varying steel gauges. Two types of members were tested as depicted in FIGS. 7 a and 7 b; the “standard” section was a 1½-inch inner flange and 2¾-inch outer flanges, and the Heavy Duty “HD” section with both inner and outer flanges of 2¾-inches.

The specimens were placed in a hydraulic compression testing machine so as to have a 10-foot, 0-inch span between the centers of support bearings. Those bearings consisted of a round bar rocker bearing. The assemblies were loaded in a two-point configuration parallel to the strong axis with steel plate and round bar bearings at the load points which were set 28 inches apart straddling the mid-span of the member. A steel spreader beam spanned between the load points and was in turn loaded at a single mid-point location with a 10,000 pound capacity load cell. A dial gauge was used to determine the deflection of the assembly at mid-span. This configuration develops a constant bending moment in the center area between load points.

The assemblies were loaded continuously until failure while load and deflection readings were taken at 200 pound increments of load. Failure was indicated when the assembly would no longer resist increasing load. Three identical specimens were tested for each of six combinations of section and steel gauge from 33 millimeters through 68 millimeters A control specimen was also tested which consisted of two standard stud sections 600S162-54 welded together in a typical bundled stud configuration. In all a total of 19 specimens were tested. To control lateral deflection and torsional distortion, lateral bracing was provided at the two load points and at the end supports. At the load points, this bracing consisted of vertical rollers so as to prevent resistance to vertical movement.

At the failure load, all assembly test specimens exhibited the same mode of distortion and failure. The compression flanges yielded and buckled along with a small portion of the side webs. As compression built up in the flanges, the outer flange distorted outward between the fasteners but the inner flange was restrained from buckling by the foam and the overlap of the outer flange. Failure occurred in all specimens when the inner flange buckled into the foam core. All specimens failed in flexure in the center area between the loading points, i.e. the constant bending moment region of the assembly. No distortion of any sort was noted outside the center region.

The North American Specification of the Design of Cold-Formed Steel Structural Members (AISI S100-2007) sets forth, a methodology by which testing results can be used to establish member strength. The average of the three failure loads for each group of specimens was used as the representative loading capacity at failure. The failure moment was then determined from that load and the assembly loading configuration. Allowable Moment for the different specimens tested was developed based on Section F1.2 of the AISI S100-2007 code: Allowable Strength Design. A safety factor was determined in accordance with Eq F1.2-2 of the code where the resistance factor from testing was used based on calculation of Eq F1.1-2 of the code. Effective section properties producing allowable moments were then calculated for the individual pieces considering them as track type elements with unstiffened flanges. The plate buckling coefficient, k, for each flange of the composite structural elements were then determined based on the effective section properties formulas and the test data. One set of k values for the inner and outer flanges was determined for the 33 and 43 mils products while a separate set was determined for the 54 and 68 mil products based on the results of the testing. These were then used to determine the allowable properties of 4-inch, 6-inch, and 8-inch deep members.

The test data showed that the Heavy Duty assembly members are stronger than two bundled 600S137 studs of the same gage. Additionally, both the Standard and Heavy Duty assembly members, as tested with the foam core, are stronger than calculated values of just the cold-formed steel pieces themselves. Tested members with thinner gages of 33 and 43 mils showed a minimum of a 20 percent increased moment capacity while tested members with gages of 54 and 68 mils showed a minimum increase of 8 percent. FIG. 8 provides the summary of the gross and effective section properties including Allowable Moment (Ma) and Allowable Shear (Va) capacities of the entire family of assembly sections in 4-inch, 6-inch, and 8-inch depths.

This testing program established the bending moment capacity at failure of 18 assembly specimens and one bundled stud beam. The failure modes were very consistent with all assembly members failing in the same manner—compression flange yielding/buckling. The load deflection curves were very linear until close to failure. Using the average failure loading from each group, the moment capacity was calculated and compared to the moment capacity derived by calculation for disconnected steel sections of the same shape. In all cases, the moment capacity of the tested shapes, when reduced by appropriate safety factors, exceeded that of the bare, disconnected shapes. This indicated that significant increase in strength is provided by the combination of the foam core and the overlapped and fastened flanges. The foam core and the overlapped flange configuration serve to delay the onset of flange buckling and thus increase the overall bending strength of the composite section. The bending strength of the assembly sections also compares favorably with that of traditional jamb member made of two standard wall studs of the same gauge steel welded in a boxed configuration.

While the present invention has been described in the context of the embodiments illustrated and described herein, the invention may be embodied in other specific ways or in other specific forms without departing from its spirit or essential characteristics. Therefore, the described embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing descriptions, and all changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

1. A method of constructing a blast resistant building element having a compressed polymer foamed core, the method comprising: bending a first elongated sheet-metal piece to form a surrounding track, having a surrounding track web integrally connected to a pair of spaced apart and outwardly extending surrounding track sidewalls to thereby define a first generally U-shaped profile; bending a second elongated sheet-metal piece to form an internal track having an internal track web integrally connected to a pair of spaced apart and outwardly extending internal track sidewalls to thereby define a second generally U-shaped profile; applying an adhesive to at least one of the surfaces within the generally U-shaped internal track; positioning a block of foamed polymer within the first generally U-shaped internal track, the block of foamed polymer being slightly larger than the space defined by the internal track web and its pair of spaced apart and outwardly extending internal track sidewalls; positioning the surrounding track about the internal track, and compressing the tracks together to yield the blast resistant building element having the compressed polymer core.
 2. The method of claim 1, further comprising coupling the surrounding and internal track in a compressed position.
 3. The method of claim 2, wherein coupling the surrounding and internal track comprises applying a plurality of pins along a first face of the building element.
 4. The method of claim 3, wherein the pins extend through adjoining surrounding and internal track sidewalls and into the core.
 5. The method of claim 3, wherein coupling the surrounding and internal track comprises applying a plurality of pins along a second opposing face of the building element.
 6. The method of claim 1, wherein the core comprises polystyrene.
 7. The method of claim 1, wherein the surrounding track sidewalls extend past the internal track web in the formed building element.
 8. A blast resistant building element having a compressed polymeric foamed core, the element comprising: an internal track having an internal track web integrally connected to a pair of spaced apart and outwardly extending internal track sidewalls so as to define a first generally U-shaped profile; a surrounding track having a surrounding track web integrally connected to a pair of spaced apart and outwardly extending surrounding track sidewalls so as to define a second generally U-shaped profile; and a compressed polymeric foamed core disposed within the internal track, wherein the compressed polymeric foamed core exerts a force against a portion of internal surfaces of the internal track and surrounding track.
 9. The blast resistant building element of claim 8 further comprising an adhesive layer surrounding a portion of the core and coupling a portion of the core to an internal portion of the internal and surrounding tracks.
 10. The blast resistant building element of claim 8, further comprising a plurality of pins on a first set of opposing faces extending through adjoining surrounding and internal track sidewalls and into the core.
 11. The blast resistant building element of claim 8, wherein the core comprises polystyrene.
 12. The blast resistant building element of claim 8, wherein the surrounding track sidewalls extend past the internal track web. 